Opalizing involves making a deposit of a light-diffusing white product such as titanium dioxide, silica or alumina, the deposit having a sufficient adherence to the bulb and a suitable thickness to effect the desired light diffusion.
Various methods of opalizing light bulbs have been proposed. The industrial process now used consists in filling a bulb with a titanium dioxide suspension which, after evacuation, leaves on the glass surface a white deposit that is dried at a temperature of 400.degree. to 500.degree. C.
Gaseous methods have been proposed but these are few and do not seem to have been industrialized. There can be cited the formation of titanium dioxide deposits by hydrolysis of titanium compounds such as titanium tetrachloride, according to U.S. Pat. No. 3,352,703. Alumina deposits can be obtained by combustion of organic aluminum compounds dissolved in a solvent by applying the teaching of U.S. Pat. Nos. 3,842,306 and 3,868,266. General Electric Co. described providing a silica deposit by combustion of tetraethyl silicate in U.S. Pat. No. 3,109,747 according to a relatively complex multistage process.
French Pat. No. 961,085 relates to making diffusing glasses by application on the inside face of fine particles of amorphous silica, the depositing of which is performed by combustion on the inside of the bulb of an organic silicon compound in the presence of oxygen.